Can good fungi restore bad soil?

Tarah Sullivan is fascinated by fungi, especially the ones in agricultural soils that offer hope for addressing toxicity issues by transforming harmful metals.

As a new assistant professor of soil microbiology in the WSU Department of Crop and Soil Sciences, Sullivan is busy setting up her laboratory to study how soil microbes can transform toxic metals like aluminum, cadmium, or lead into less toxic forms, and how they can help plants take up essential micronutrients like iron, zinc, and copper.

Fungi on the surface of lead shot transform lead minerals into a less toxic form. Photo by Geoff Gadd.

“One idea that gets people excited is the possibility that beneficial fungi could help address the increasing soil acidification and aluminum toxicity problems found in the Palouse,” Sullivan said. In the last 50 years, soil acidity has increased due to the use of nitrogen fertilizers. The bad news is that soil acidity can cause dramatic decreases in yields, in many locations up to 50 percent or more for sensitive crops, such as garbanzos, lentils, wheat, and barley, according to Sullivan.

Soil acidity transforms naturally-occurring aluminum into a soluble form that is more available to plants and which damages their roots. A common though costly solution to aluminum toxicity is to reduce soil acidity by applying lime to soil. But the effects are often short lived.

The good news is that fungi are plentiful and tolerant of acidic soils, and many are even well-suited for remediation of metals. According to Sullivan, as soils become more acidic, fungi can comprise more than 75 percent of soil microbes by mass — and most are the good guys.

Tarah Sullivan and Geoff Gadd. Photo by Shelly Hanks, WSU.

“There are hundreds of billions of microbes in one gram of soil. An extremely small proportion of them are pathogens. The vast majority of soil microbes are beneficial and we don’t fully understand those,” Sullivan said.

Many species of fungi associated with plant roots, called mycorrhizal fungi, have been shown to decrease aluminum toxicity in plants. Sullivan wants to know how we can enhance these beneficial soil fungal populations in the field and how we can promote their metal-detoxifying activities.

She hopes to identify specific fungi that have the aluminum buffering qualities, and then see if it’s possible to inoculate the soil with them to extend the benefits of liming. She also hopes to discover whether it’s possible to create soil conditions that favor the beneficial fungi by adding soil amendments, such as compost or straw.

Ultimately, Sullivan believes her research will contribute to a sustainable approach to mitigating soil acidification problems in the Palouse, providing a more environmentally friendly and economically viable long-term strategy.

Sullivan holds a doctorate in soil microbiology from Cornell University and comes to WSU following postdoctoral research at Oak Ridge National Laboratory where she focused on soil fungal communities in a lead-contaminated military site. She recently hosted a Department of Crop and Soil Sciences seminar presented by Geoffrey Michael Gadd, an internationally known geomycologist from the University of Dundee in Scotland who studies how fungi transform the chemical composition of rocks and minerals.